Dental enamel is highly mineralized hard tissue that is formed by the epithelial ameloblasts, and is initially secreted as extracellular matrix that contains a complex mixture of unique proteins. The apparently well-controlled cell and matrix interactions, which are responsible for enamel development and biomineralization, are not well understood. Ingestion of fluoride can interfere with enamel formation, causing a delay in the removal of amelogenin proteins from the maturing matrix, resulting in more porous mature enamel. The studies proposed in this application have evolved from the Principal Investigator's on going interest in the mechanisms of fluorosis. In this proposal, two possible mechanisms for dental fluorosis will be tested, including a differential binding of enamel proteins to fluoride containing apatite, and a direct effect of fluoride on ameloblast function. The specific aims are: 1) to measure the major mineral components of fluoride human enamel, and to synthesize fluoride-containing carbonated hydroxyapatite based on these determinations; 2) to compare the relative binding of enamel matrix proteins to hydroxyapatite, carbonated hydroxyapatite, and fluoride-containing carbonated hydroxyapatite; 3) to determine whether fluoride alters mRNA expression, protein secretion, or proteinase activity from ameloblast-like cells in vitro; 4) to develop human ameloblast cell lines. The aims outlined in this proposal will allow for determining how fluoride can affect developing enamel, and the mechanisms that are responsible for the formation of fluorosed enamel.